Automotive brake disks are periodically resurfaced by a disk brake lathe in order to maintain proper operation of the brakes in service. The disk brake lathe typically has a pair of cutting tools, each attached to a tool holder by a fastener to allow replacement when the cutting tool becomes worn. The tool holders position the cutting tools against the surfaces of the brake disk to establish a desired depth of cut, and then maintain the cutting tools in position as they are drawn across the disk surfaces while the lathe rotates the brake disk in order to machine the disk surfaces. Typically, the desired depth of cut is set and the cutting tools are positioned near the center of the brake disk to begin the machining process. The cutting tools are then moved radially outwards to resurface the brake disk.
Vibrations caused by the cutting action of the cutting tools on the disk surfaces need to be attenuated, both to reduce chattering of the cutting tools to assure that the resulting machined disk surfaces are sufficiently planar for proper operation, and to reduce undesirable noise in the machining environment. One approach to reducing vibrations has been the use of friction pads which are biased against the disk surfaces by a spring. The friction pads engage the cutting tools, the tool holders, and/or the fasteners so as to move with the cutting tools across the disk surfaces. Such devices are taught in U.S. Pat. Nos. 3,710,661; 4,531,434; 5,297,460; 6,227,085; 6,553,877; and 6,591,720.
One limitation of this technique is that the pads wear as they rotate against the disk surfaces, and thus their effectiveness in attenuating vibrations diminishes as a function of time, since the spring force will diminish as the pads wear. This problem compounds as the thickness of the friction pads increases, since employing a spring which provides sufficient pressure at or near the time when the pads are to be discarded will apply excessive pressure when the friction pads are new, accelerating wear of the friction pads. Similarly, if the spring force is adjusted so as to apply a practical amount of pressure when the pads are new, the pressure applied by the spring may be inadequate when the pad has experienced substantial wear but is not yet worn to the point were it needs to be discarded. Thus, there is a need for a vibration attenuator where the force can be varied to better suite the situation and to compensate for wear of the pads.